Machinable nonmagnetic high-resistance cast-iron alloy



STANLEY ERNEST DAWSON, F DAVENPORT, STOCKPORT, ENGLAND, ASSIGNOR, BY

MESNE ASSIGNMENTS, "1'0 FERRANTI METER AND TRANSFORMER UFACTUR- DIG COMPANY, LIMITED, OETORONTO, CANADA. a

IEAABLE NONMAGNETIC HIGH-RESISTANCE CAST-IRON ALLOY.

No Drawing.

Frewland Avenue, Davenport, Stockport, in

the county of Chester, England, have invented a certain new and usefulMachinable Nonmagnetic High-Resistance Cast-Iron Alloy, of which the following is a specifica- W tion.

This invention relates to an alloy having iron as its principal constituent, which 1s nonsmagnetic or nearly so, and has a high specific electrical resistance, and which resembles cast iron as regards its treatment in the foundry and by cutting tools either machine or handoperated.

Articles made of such alloy when subject to the influence of an alternatin magnetic field have only small currents mduced in them. They --may, therefore, be advantageously used instead of similar articles made of brass for use inelectrical apparatus, as thereby eddy current losses are greatly reduced.

"It is well known that an alloy having iron as its principal constituent and with a certain proportion of manganese is practically non-magnetic, but articles cast from such- 80 alloys "are too' hard to be machined by the usual workshop cutting tools and can onl be operated on by grinding. The invention consists 1n a non-magnetic or nearly non-magnetic alloy resembling ac cast iron as regards its treatment in the foundry and workshop, having a higher specific electrical resistance than cast iron, and having as its essential constituents iron, manganese or its equivalent and another a metal or metals, for examplenickel.

The invention also consists in articles made from such alloy, for use in electrical ap aratus. y p

2 suitable alloy accordingto my inventioli contains iron, manganese and nickel, in

the proportions 85, 5 and 10 respectively. It

also contains carbon, silicon and other ingredients of'mlnor or non-essential charactar as usually found in ordinary cast 1ron.

The alloys made according to my invention Application filed November 25, 1921. Serial No. 517,777.

give the desired non-magnetic quality, and nickel in such proportion as to counteract the hardening effect of the manganese and render the alloy susceptible to treatment by cutting toolsas is cast iron. The presence of nickel reduces the amount of manganeseotherwise necessary to make the alloy nonmagnetic. iron and manganese requires a much greater proportion of manganese to make it nonmagnetic than do alloys made according to my invention. In fact, the known ironmanganese alloys with a high percentage of An' alloy consisting mainly ofv manganese do not possessanything like the same degree of non-magnetic quality as does an alloy made according to my invention with the proportions stated above.

An alloy of the proportions stated above is practically non-magnetic, has a specific electrical resistance nearly twice that of ordinary cast iron, twenty times that of brass, or-one hundred times that of pure copper. Its tensile strength is about 14.5 tons per square inch, and its ductility is superior to thatofcast iron. It has a very close grain, and can be machined as easily as soft cast iron. The softness can be increased by increasing the nickel content.

For articles in which the highest possible degree of non-magnetic quality is not essential a less. costly alloy can be used. As an example, the following relative proportions can be used :iron 90, manganese 5, nickel 5.

One method of producing an alloy according to my invention consists in melting the metals other than cast iron (that is, manganese and nickel) in a crucible and adding such molten metal to ordinary molten cast iron as it flows into the ladle from the spout of the cupola in which it has been melted- Having now described my invention, what I claim as new and desire to secure by Let- 'ters Patent is 1. A practically non-magnetic machinble cast iron like alloy containing manganese in amount to render the alloy substantially non-magnetic, the balance of the alloy being principally of cast iron, and a metal to render the alloy machinable.

2. A practically non-magnetic cast ironlike alloy containing manganese in amount to render the alloy substantiall 'non-magnetic, the balance of the alloy being princiallyof cast iron ancl nickel to render the al 0y machinahle.

3; An article for use in electrical an aratus made of non-magnetic machina le cast iron-like alloy containin manganese in amount to render the alloy s11 stantially nonmagnetic, the balance of the alloy being principallly of cast iron and a metal to ren- &er the al 0y machinable.

4:. A practically non-ma etic machinalole cast iron alloy inclniing row. 5 to 14% of nickel, between 3 and 7% of manganese. and at least 80% of-gi'ey cast iron.

5. A practically nonma etic machinalole cast iron alloy as -claime in claim 4:, in M which the'cast iron contains at least 2.5% of carbon and at least 1.5% of silicon.

6. A practically non-magnetic machinalile cast iron alloy including 85 of iron, at least 1.5% of silicon, 5% of manganese and to 10% of nickel.

7. Articles for use in electrical apparatus made from an allo as claimed in claim 4.

In testimony w erect I have signed my name to this specification.

STANLEY ERNEST DAWSON. 

